The present invention refers to data processing systems, and more particularly to a data processing system that is suitable for use with a technology to distribute and store journals in a plurality of sites.
The data processing system is demanded to prevent data loss in a storage system during disaster or the like. To this end, a technology to duplicate data in a storage system located in a remote place has a significant meaning. Note that the storage system referred to herein includes storage devices such as a storage controller and a disk drive.
A technology to duplicate data stored in a storage system to another storage system is disclosed in U.S. Pat. No. 6,324,654. This patent further discloses a technology wherein, upon receipt of a write system call, a device driver of the OS of a computer (hereinafter referred to as a “primary host”) incorporated in a first system writes data to a local data device and stores update log in a write log device, a program of the primary host transfers updated log to a program of a computer (hereinafter referred to as a “secondary host”) incorporated in a second system, and data of a data device of the second system is updated based on the update log information received by the program of the secondary host.
In the above-stated prior art, data stored in respective storage systems of the primary host and the secondary host is transferred between the two hosts. At this time, the hosts are used as transport paths of the data. Since the data stored in the storage systems are transferred via a communication link between the hosts, the prior art had problems that the CPU loads of the respective hosts, channel loads, and traffics in a line connecting the hosts are increased. Further, the prior art had another problem that, since no considerations are given on load balancing of the devices that occurs due to log sampling, log writing processes and log reading processes concentrate on the write log device.
The present invention has been made to solve above-stated problems of the prior art, and an object of the present invention is to provide a data processing system capable of recovering data by sampling data update logs, which is able to assure data consistency in a plurality of sites without deteriorating its processing capability by giving no load on hosts and a network, and avoiding centralized loads on a specific storage device due to data update or recovery.